Study On Gypsum-based Modified Raw Soil Building Materials

Earth architecture is one of the oldest and it is still in use.In recent years,the protection of ecology and energy conservation have become a hot topic in society.Due to its unique ecological energy conservation and humanistic art,the earth architecture has attracted people's attention.Traditional soil materials have problems such as poor mechanical properties,poor water resistance,and large drying shrinkage,which severely restricts the promotion and application of soil materials.In view of the shortage of raw materials,strengthening its modified research to improve its performance have vital practical significance in expanding the application scope,improving service efficiency and reducing the cost etc.Effective modification of the soil material should significantly improve its performance,and the modification methods should be ecological and economically feasible.In this paper,the effects of modified components such as gypsum,fly ash,water reducing agent and pH adjusting components on the working properties,mechanical properties and water resistance of raw soil materials were studied.The test found that the higher the gypsum content,the faster the raw soil materials and the higher the strength,but the gypsum content exceeds a certain range,the strength of the soil material is not improved,and the gypsum modified soil material has poor water resistance;The amount of fly ash can improve the strength of the modified raw soil material,but when the amount of fly ash is too high,the strength of the modified raw soil material will decrease,and the fly ash can improve the water resistance of the raw soil material;water-reducing agent can improve the fluidity and the mechanical properties of the soil material,it can also increase the water resistance of the soil material,and the organic water-reducing agent improves the performance of the soil material;the addition of the pH adjusting component to the modified soil material can improve the work performance,mechanical properties and water resistance of raw soil materials.In this paper,the suitable ratio of gypsum-based modified raw soil materials is: 15% gypsum,5% fly ash,1% pH adjusting component,1% polycarboxylic acid water reducing agent.The soil material has a large fluidity and a suitable setting time.It is found that the early strength of gypsum-based modified soil material develops rapidly,and the strength development becomes slower in the later curing age;the compressive strength is up to 9.3 MPa,the flexural strength is up to 3.5 MPa,and the modified soil material has good water resistance.After demolding for 1 d,it can be immersed in water.After 28 d of natural curing,the strength loss of the soaking water for 24 h is only about 40%,and the mass loss is less than 1%.The higher the moisture content of the modified raw material,the lower the strength;and strength is becoming lower when adding the soaking time,and the loss of strength after soaking water is unrecoverable;the dry-wet cycle performance of the modified soil material is obviously improved,and the strength and mass loss will increase as the number of dry-wet cycles increases;the shrinkage rate is finally stabilized between 0.06% and 0.07%,and the shrinkage mainly occurs at early curing age;the modified components do not change the mineral composition of the clay particles,and the modified raw soil materials still have good ecological properties.